Modern communications networks generally include a multiplicity of paths or links that are interconnected to route voice, video and data (hereinafter collectively referred to as "data") traffic from one location of the network to another. At each location, an interconnect node or office couples a plurality of sources and destinations to the network. In some cases, the sources and destinations are incorporated in a private line network that includes a series of offices connected together by leased-lines with switching facilities and transmission equipment owned and operated by the carrier and leased to the user. This type of network is conventionally referred to as a circuit-switching network. Accordingly, a source of one office at one location of the network may transmit data to a destination of a second office located at another location of the network through their respective switching facilities.
Generally, at any given location, since a large number of sources desire to communicate through their respective switching facilities to destinations at various other locations of the network, the data traffic from the various sources is first multiplexed through the source switching facility, then demultiplexed at the destination switching facility and finally delivered to the proper destination. A variety of techniques for efficiently multiplexing the data from multiple sources onto a single circuit of the network are presently employed in private line networks. For instance, time division multiplexing ("TDM") affords each source full access to the allotted bandwidth of the circuit for a small amount of time. The circuit is thus divided into time segments corresponding to specific sources to provide for the transfer of data from those sources, when called upon, through the network. Multiplexing techniques, such as TDM, significantly increase the throughput of data throughout the private line network.
Other data communications systems, in contrast, have not been as successful employing multiplexing techniques to enhance network efficiency further. In particular, frame-relay networks offer far fewer alternatives than their circuit-switching network counterparts. Frame-relay networks are often referred to as packet-switching networks. Packet-switching networks, as opposed to circuit-switching networks, allow multiple users to share the data network facilities and bandwidth rather than providing a specific amount of dedicated bandwidth to each user, as in TDM. Packet switches divide bandwidth into connectionless, virtual circuits. Virtual circuit bandwidth is only consumed when data are actually transmitted; otherwise, the bandwidth is not used. While packet-switching networks may appear to mirror the operation of a statistical multiplexer (whereby multiple logical users share a single network access circuit), there is still room for improving network throughput efficiency in frame-relay and other packet-switching networks.
For instance, a one-to-one correspondence exists between applications and frame-relay virtual circuits, there being no inherent mechanism in today's frame-relay standards for transport of end-to-end data management. Internet Engineering Task Force Request for Comments ("IETF RFC") 1490 "Multiprotocol Interconnect Over Frame Relay," as herein incorporated by reference, provides the ability to multiplex protocols, but forces the equation of a protocol to a single logical channel on a given virtual circuit. Additionally, IETF RFC 1490 protocol headers must appear on every single frame transmitted over the circuit, without exception.
Accordingly, what is needed in the art is a circuit, method and system for multiplexing frames from different sources onto a single frame-relay virtual circuit. The system and method must be proficient at various levels of capabilities or modes, and no additional restrictions shall be placed on the format of the data carried by the virtual circuit.